Lubricating Composition Containing Viscosity Modifier Combination

ABSTRACT

The present invention relates to a lubricating composition containing (a) an oil of lubricating viscosity, (b) a star polymer and (c) a substantially linear polymer with a weight average molecular weight of 45,000 or less. The invention further provides a method of lubricating a mechanical device, typically a manual transmission with the lubricating composition. The invention further provides for the use of the lubricating composition to provide a number of benefits including lower operating temperatures and fuel economy.

FIELD OF INVENTION

The present invention relates to a lubricating composition containing(a) an oil of lubricating viscosity, (b) a star polymer and (c) asubstantially linear polymer with a weight average molecular weight of45,000 or less. The invention further provides a method of lubricating amechanical device, typically a manual transmission with the lubricatingcomposition. The invention further provides for the use of thelubricating composition to provide a number of benefits including loweroperating temperatures and fuel economy.

BACKGROUND OF THE INVENTION

Viscosity index improvers are known to be added to lubricating oilcompositions to improve the viscosity index of the lubricant. Typicalviscosity index improvers include polymers of methacrylates, acrylates,olefins (such as copolymers of alpha-olefins and maleic anhydride andesterified derivatives thereof), or maleic anhydride-styrene copolymers,and esterified derivatives thereof. The viscosity index improvers tendto incorporate ester functional groups in pendant/grafted/branchedgroups. The ester functional groups may be derived from linear alkylalcohols with 1 to 40 carbon atoms. Recent attempts have been made toproduce viscosity index improvers from copolymers of alpha-olefins.However, such viscosity index improvers have poor shear stability, toohigh a viscosity at low temperature, poor fuel economy, and poornon-dispersant cleanliness.

In addition, lubricants capable of performing at lower viscosity (in,for instance, driveline devices) typically provide increased fueleconomy (thus improving corporate average fuel efficiency (CAFE), NEDC(European Driving Cycle), or FTP-75 (Federal Test Procedure), orJapanese test cycle (JC-08)). Conversely, higher viscosity fluidscontribute to elevated gear and transmission operating temperatures,which are believed to reduce fuel economy and diminish durability.

International publication WO 2007/127660 discloses a lubricatingcomposition containing a star polymer, a phosphorus-containing compoundand an extreme pressure agent.

International publications WO2006/047398 and WO2006/047393:WO2006/047398 discloses that the star polymer may be derived from atomtransfer radical polymerisation (ATRP), nitroxide mediatedpolymerisation, anionic polymerisation and reversible additionfragmentation (RAFT). WO2006/047393 discloses lubricating compositionshaving linear and star poly(meth)acrylates derived from RAFTpolymerisation.

International Patent Application PCT/US2009/052028 discloses alubricating composition containing a copolymer comprising units derivedfrom monomers (i) an α-olefin and (ii) an ethylenically unsaturatedcarboxylic acid or derivatives thereof esterified with a primary alcoholbranched at the β- or higher position, wherein the copolymer, prior toesterification has a reduced specific viscosity of up to 0.08.

US Patent Application 2008/0085847 discloses a lubricating oilcomposition comprising a major amount of oil of lubricating viscosity,and a viscosity index (VI) improver composition comprising a firstpolymer comprising an amorphous ethylene-α olefin copolymer orethylene-α-olefin-diene terpolymer having a crystallinity of not greaterthan about 1.0%; and a second polymer comprising a star polymer, thearms of which are derived from diene, and optionally vinyl aromatichydrocarbon monomer, wherein the star polymer has a Shear StabilityIndex (SSI) of from about 1% to about 35% (30 cycle).

SUMMARY OF THE INVENTION

The inventors of this invention have discovered that a lubricatingcomposition, method and use as disclosed herein is capable of providingat least one of improved oxidative stability, reduced mechanical deviceoperating temperatures, increased mechanical device durability, improvedshear stability index, improved viscosity index, improved lowtemperature viscometrics and improved high temperature viscometrics.

In one embodiment the invention provides a lubricating compositioncomprising (a) an oil of lubricating viscosity, (b) a star polymer, and(c) a substantially linear polymer with a weight average molecularweight of 45,000 or less, or 35,000 or less, or 25,000 or less, or 8000to 25,000, or 12,000 to 20,000.

The substantially linear polymer may have a shear stability index ofless than 25 (or 15 or less, or 10 or less, or 0 to 10, or 0 to 5) asmeasured by procedure described in CEC test CEC-L-45-99 entitled“Viscosity Shear Stability of Transmission Lubricants (Taper RollerBearing Rig)” or test method DIN 51350-6-KRL/C.

In one embodiment the invention provides a lubricating compositioncomprising (a) an oil of lubricating viscosity, (b) a star polymer, and(c) a substantially linear polymethacrylate polymer with a weightaverage molecular weight of 45,000 or less, or 35,000 or less, or 25,000or less, or 8000 to 25,000, or 12,000 to 20,000.

In one embodiment the invention provides a lubricating compositioncomprising (a) an oil of lubricating viscosity, (b) a star polymer, and(c) a copolymer comprising units derived from monomers (i) an α-olefinand (ii) an ethylenically unsaturated carboxylic acid or derivativesthereof esterified with an alcohol.

In one embodiment the invention provides a lubricating compositioncomprising (a) an oil of lubricating viscosity, (b) a star polymer, and(c) a copolymer comprising units derived from monomers (i) an α-olefinand (ii) an ethylenically unsaturated carboxylic acid or derivativesthereof esterified with a primary alcohol branched at the β- or higherposition, wherein the copolymer, prior to esterification has a reducedspecific viscosity of up to 0.2, or up to 0.15, or up to 0.10, ortypically up to 0.08.

In one embodiment the invention provides a lubricating compositioncomprising:

(a) an oil of lubricating viscosity,

(b) a star polymer, wherein the star polymer may be a polymethacrylateor polyacrylate (typically a polymethacrylate), the star polymer may bederived from a monomer composition comprising:

-   -   (i) 50 wt % to 100 wt % (or 65 wt % to 95 wt %) of an alkyl        methacrylate, wherein the alkyl group of the methacrylate has 10        to 30, or 10 to 20, or 12 to 18, or 12 to 15 carbon atoms;    -   (ii) 0 wt % to 40 wt % (or 5 wt % to 30 wt %) of an alkyl        methacrylate, wherein the alkyl group of the methacrylate has 1        to 9, or 1 to 4 carbon atoms (for example methyl, butyl, or        2-ethylhexyl); and    -   (iii) 0 wt % to 10 wt % (or 0 wt % to 5 wt %, or 0.1 to 2 wt %)        of a dispersant monomer (may be referred to as either        oxygen-containing compound, or nitrogen-containing monomer and        typically nitrogen-containing monomer); and

(c) copolymer comprising units derived from monomers (i) an α-olefin and(ii) an ethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher position,wherein the copolymer, prior to esterification has a reduced specificviscosity of up to 0.2, or up to 0.15, or up to 0.10, typically up to0.08.

In one embodiment the invention provides a lubricating compositioncomprising an oil of lubricating viscosity, a star polymer and acopolymer comprising units derived from monomers (i) an α-olefin and(ii) an ethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher position,wherein the copolymer is an interpolymer, and wherein the interpolymerhas a reduced specific viscosity (prior to esterification) of up to0.08, or 0.02 to 0.08 (or 0.02 to 0.07, 0.03 to 0.07 or 0.04 to 0.06).

The copolymer comprising units derived from monomers (i) an α-olefin and(ii) an ethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher positionmay be defined in terms of weight average molecular weight or by RSV.Typically the weight average molecular weight is measured on the finalesterified copolymer, optionally capped with an amine. The weightaverage molecular weight may be 5000 to 35,000 (approximately 0.15 RSV),or 5000 to 20,000, or 13,000 to 18,000.

The copolymer reduced specific viscosity (RSV) is measured by theformula RSV=(Relative Viscosity−1)/Concentration, wherein the relativeviscosity is determined by measuring, by means of a dilution viscometer,the viscosity of a solution of 1.6 g of the copolymer in 100 cm³ ofacetone and the viscosity of acetone at 30° C. A more detaileddescription of RSV is provided below. The RSV is determined for thecopolymer of an α-olefin and (ii) an ethylenically unsaturatedcarboxylic acid or derivatives thereof before esterification with theprimary alcohol branched at the β- or higher position.

In different embodiments the primary alcohol branched at the β- orhigher position may have at least 12 (or at least 16, or at least 18 orat least 20) carbon atoms. The number of carbon atoms may range from atleast 12 to 60, or at least 16 to 30.

In one embodiment the invention provides a lubricating compositioncomprising an oil of lubricating viscosity, a star polymer and acopolymer comprising units derived from monomers (i) an α-olefin and(ii) an ethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher position,wherein the copolymer may be an interpolymer, and wherein theinterpolymer has a reduced specific viscosity of up to 0.08, or 0.02 to0.08 (or 0.02 to 0.07, 0.03 to 0.07 or 0.04 to 0.06).

In one embodiment the copolymer comprising units derived from monomers(i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof esterified with a primary alcohol branched at the β-or higher position described above further comprises units from amonomer having at least one of an ester group and a nitrogen containinggroup (such as amino-, amido- and/or imido-group), typically sufficientto provide 0.01 wt % to 1.5 wt % (or 0.02 wt % to 0.75 wt %, or 0.04 wt% to 0.25 wt %) nitrogen to the copolymer.

In one embodiment the invention provides for a method of lubricating amechanical device comprising supplying to said mechanical device(typically a driveline device) a lubricating composition as disclosedherein. In one embodiment the mechanical device may be a manualtransmission.

In one embodiment the invention provides for the use of a lubricatingcomposition as described herein to provide a lubricant (typically amanual transmission lubricant) with at least one (or at least two, or upto all) of acceptable or improved shear stability, acceptable orimproved viscosity index control, acceptable or improved low temperatureviscosity, acceptable or improved fuel economy, and acceptable orimproved device operating temperatures. Typically the lubricant may beused in a driveline device such as a manual transmission.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a lubricating composition, method and useas disclosed herein.

Star Polymer

The lubricating composition of the invention contains a star polymer (orthe star polymer may also be referred to as a radial polymer). The starpolymer may be present in the compositions described herein at 0.1 wt %to 30, or 0.1 wt % to 20 wt %, wt %, or 2 wt % to 30 wt %, or 5 wt % to20 wt %, or 8 wt % to 15 wt %. The star polymer may also be present at0.2 wt % to 15 wt %, or 0.5 wt % to 10 wt %, or 1 wt % to 8 wt % of thelubricating composition.

A detailed description of the star polymer disclosed herein may also bedescribed in WO 2007/127660 (published on 8 Nov. 2007, by Baker et al.and assigned to The Lubrizol Corporation), paragraphs [0021] to [0061].Baker discloses composition and methods of preparation of a variety ofstar polymers.

In one embodiment the star polymer may be a polymer derived from greaterthan 50 wt % or more of a non-diene monomer.

In different embodiments the star polymer may contain greater than 50 wt%, or 55 wt % or more, or 70 wt % or more, or 90 wt % or more, or 95 wt% or more, or 100 wt % of a non-diene monomer (that is to say, non-dienemonomer units or units derived from polymerisation of one of morenon-diene monomers). Examples of diene monomers include 1,3-butadiene orisoprene. In contrast, examples of a non-diene of the present inventionmay include styrene, methacrylates, acrylates, or mixtures thereof. Inone embodiment the star polymer may be a polymer derived frommethacrylates, or mixtures thereof.

As described hereinafter the molecular weight of the viscosity modifierhas been determined using known methods, such as GPC analysis usingpolystyrene standards. Methods for determining molecular weights ofpolymers are well known. The methods are described for instance: (i) P.J. Flory, “Principles of star polymer Chemistry”, Cornell UniversityPress 91953), Chapter VII, pp 266-315; or (ii) “Macromolecules, anIntroduction to star polymer Science”, F. A. Bovey and F. H. Winslow,Editors, Academic Press (1979), pp 296-312. As used herein the weightaverage and number average molecular weights of the polymers of theinvention are obtained by integrating the area under the peakcorresponding to the star polymer of the invention, which is normallythe major high molecular weight peak, excluding peaks associated withdiluents, impurities, uncoupled star polymer chains and other additives.

The star polymer may have a weight average molecular weight of 100,000to 1,000,000, or 125,000 to 700,000, or 150,000 to 500,000, or 200,000to 400,000. The weight average molecular weight of an arm of the starpolymer may be in the range of 8,000 to 150,000, or 10,000 to 100,000 or15,000 to 75,000, or 25,000 to 70,000.

As used herein the shear stability index (SSI) of the star polymer maybe determined by a 20 hour KRL test (Volkswagen Tapered Bearing RollerTest). The test procedure is set out in both CEC-L-45-A-99 or equivalenttest method DIN 51350-6-KRL/C.

The star polymer SSI may be in the range of 0 to 100, or 0 to 80, or 0to 60, or 0 to 50, 0 to 20, or 0 to 15, or 0 to 10, or 0 to 5. Anexample of a suitable range for the SSI includes 1 to 5, or 25 to 65.

The star polymer may be a homopolymer or a copolymer, that is, its armsmay be homopolymeric or copolymeric. In one embodiment the star polymermay be a copolymer. The star polymer may be a star polymer having arandom, tapered, di-block, tri-block or multi-block architecture.Typically the star polymer has random or tapered architecture.

The star polymer may have arms that may have a block-arm architecture,or hetero-arm architecture, or tapered-arm architecture. Tapered-armarchitecture has a variable composition across the length of a starpolymer arm. For example, the tapered arm may be composed of, at oneend, a relatively pure first monomer and, at the other end, a relativelypure second monomer. The middle of the arm is more of a gradientcomposition of the two monomers.

The star polymer derived from a block-arm typically contains one or morestar polymer arms derived from two or more monomers in block structurewithin the same arm. A more detailed description of the block-arm isgiven in Chapter 13 (pp. 333-368) of “Anionic Polymerization, Principlesand Practical Applications” by Henry Hsieh and Roderic Quirk (MarcelDekker, Inc, New York, 1996) (hereinafter referred to as Hsieh et al.).

The star polymer typically has architecture such that the arms may bechemically bonded to a core portion. The core portion may be apolyvalent (meth)acrylic monomer, oligomer, polymer, or copolymerthereof, or a polyvalent divinyl non-acrylic monomer, oligomer polymer,or copolymer thereof. In one embodiment the polyvalent divinylnon-acrylic monomer may be divinyl benzene. In one embodiment thepolyvalent (meth)acrylic monomer may be an acrylate or methacrylateester of a polyol or a methacrylamide of a polyamine, such as an amideof a polyamine, for instance a methacrylamide or an acrylamide. Indifferent embodiments the polyvalent (meth)acrylic monomer may be (i) acondensation reaction product of an acrylic or methacrylic acid with apolyol or (ii) a condensation reaction product of an acrylic ormethacrylic acid with a polyamine.

The polyol which may be condensed with the acrylic or methacrylic acidin one embodiment contains 2 to 20 carbon atoms, in another embodiment 3to 15 carbon atoms and in another embodiment 4 to 12 carbon atoms; andthe number of hydroxyl groups present in one embodiment may be 2 to 10,in another embodiment 2 to 4 and in another embodiment 2. Examples ofpolyols include ethylene glycol, poly(ethylene glycols), alkane diolssuch as 1,6-hexane diol or triols such as trimethylolpropane,oligomerised trimethylolpropanes such as Boltorn® materials sold byPerstorp Polyols. Examples of polyamines include polyalkylenepolyaminessuch as ethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, pentaethylenehexamine, and mixtures thereof.

Examples of the polyvalent unsaturated (meth)acrylic monomer includeethylene glycol diacrylate, ethylene glycol dimethacrylate, diethyleneglycol diacrylate, diethylene glycol dimethacrylate, glyceroldiacrylate, glycerol triacrylate, mannitol hexaacrylate,4-cyclohexanediol diacrylate, 1,4-benzenediol dimethacrylate,pentaerythritol tetraacrylate, 1,3-propanediol diacrylate,1,5-pentanediol dimethacrylate, bis-acrylates and methacrylates ofpolyethylene glycols of molecular weight 200-4000, polycaprolactonedioldiacrylate, pentaerythritol triacrylate, 1,1,1-trimethylolpropanetriacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, triethylene glycol diacrylate,triethylene glycol dimethacrylate, 1,1,1-trimethylolpropanetrimethacrylate, hexamethylenediol diacrylate or hexamethylenedioldimethacrylate or an alkylene bis-(meth)acrylamide.

The star polymer with branched, comb-like, radial or star architecturemay have 2 or more arms, or 5 or more arms, or 7 or more arms, or 10 ormore arms, for instance 12 to 100, or 14 to 50, or 16 to 40 arms. Thestar polymer with branched, comb-like, radial or star architecture mayhave 120 arms or less, or 80 arms or less, or 60 arms or less.

The star polymer may be obtained/obtainable from a controlled radicalpolymerisation technique. Examples of a controlled radicalpolymerisation technique include RAFT, ATRP or nitroxide mediatedprocesses. The star polymer may also be obtained/obtainable from anionicpolymerisation processes. In one embodiment the star polymer may beobtained/obtainable from RAFT, ATRP or anionic polymerisation process.In one embodiment the star polymer may be obtained/obtainable from RAFTor ATRP polymerisation process. In one embodiment the star polymer maybe obtained/obtainable from a RAFT polymerisation process.

Methods of preparing polymers using ATRP, RAFT or nitroxide-mediatedtechniques are disclosed in the example section of InternationalPublication WO 2006/047398, see examples 1 to 47.

More detailed descriptions of polymerisation mechanisms and relatedchemistry is discussed for nitroxide-mediated polymerisation (Chapter10, pages 463 to 522), ATRP (Chapter 11, pages 523 to 628) and RAFT(Chapter 12, pages 629 to 690) in the Handbook of RadicalPolymerization, edited by Krzysztof Matyjaszewski and Thomas P. Davis,2002, published by John Wiley and Sons Inc (hereinafter referred to as“Matyjaszewski et al.”).

The discussion of the star polymer mechanism of ATRP polymerisation isshown on page 524 in reaction scheme 11.1, page 566 reaction scheme11.4, reaction scheme 11.7 on page 571, reaction scheme 11.8 on page 572and reaction scheme 11.9 on page 575 of Matyjaszewski et al. In ATRPpolymerisation, groups that may be transferred by a radical mechanisminclude halogens (from a halogen-containing compound) or variousligands. A more detailed review of groups that may be transferred isdescribed in U.S. Pat. No. 6,391,996, or paragraphs 61 to 65 ofInternational Publication WO 2006/047398.

In RAFT polymerisation, chain transfer agents are important. A moredetailed review of suitable chain transfer agents is found in paragraphs[0066] to [0071] of International Publication WO 2006/047398. In oneembodiment a suitable RAFT chain transfer agent includes2-dodecylsulphanylthiocarbonyl-sulphanyl-2-methyl-propionic acid butylester, cumyl dithiobenzoate or mixtures thereof. A discussion of thestar polymer mechanism of RAFT polymerisation is shown on page 664 to665 in section 12.4.4 of Matyjaszewski et al.

When the star polymer is prepared from anionic polymerisationtechniques, initiators include, for example, hydrocarbyl lithiuminitiators such as alkyl lithium compounds (e.g., methyl lithium,n-butyl lithium, sec-butyl lithium), cycloalkyl lithium compounds (e.g.,cyclohexyl lithium and aryl lithium compounds (e.g., phenyl lithium,1-methylstyryl lithium, p-tolyl lithium, naphyl lithium and1,1-diphenyl-3-methylpentyl lithium. Also, useful initiators includenaphthalene sodium, 1,4-disodio-1,1,4,4-tetraphenylbutane,diphenylmethyl potassium or diphenylmethyl sodium.

A more detailed description of process to prepare the star polymerderived from anionic processes is discussed in International PatentApplication WO 96/23012, page 3, line 11 to page 5, line 8. Page 7, line25 to page 10, line 15 of WO 96/23012 further describes methods ofpreparing polymers by anionic polymerisation techniques. A detaileddescription of anionic polymerisation process is given in Textbook ofStar Polymer Science, edited by Fred W. Billmeyer Jr., Third Edition,1984, Chapter 4, pages 88-90.

The star polymer may comprise at least one of (a) a star polymer derivedfrom monomers comprising: (i) a vinyl aromatic monomer; and (ii) acarboxylic monomer (typically maleic anhydride, maleic acid,(meth)acrylic acid, itaconic anhydride or itaconic acid) or derivativesthereof; (b) a poly(meth)acrylate; (c) a functionalised polyolefin; (d)an ethylene vinyl acetate copolymer; (e) a fumarate copolymer; (f) acopolymer derived from (i) an α-olefin and (ii) a carboxylic monomer(typically maleic anhydride, maleic acid, (meth)acrylic acid, itaconicanhydride or itaconic acid) or derivatives thereof; or (g) mixturesthereof. In one embodiment the star polymer with pendant groupscomprises a polymethacrylate or mixtures thereof.

In one embodiment the star polymer may be a poly(meth)acrylate(typically a polymethacrylate). The star polymer may be derived from amonomer composition comprising:

(a) 50 wt % to 100 wt % (or 65 wt % to 95 wt %) of an alkyl(meth)acrylate, wherein the alkyl group of the (meth)acrylate has 10 to30, or 10 to 20, or 12 to 18, or 12 to 15 carbon atoms, or mixturesthereof;

(b) 0 wt % to 40 wt % (or 5 wt % to 30 wt %) of an alkyl (meth)acrylate,wherein the alkyl group of the (meth)acrylate has 1 to 9, or 1 to 4carbon atoms (for example methyl, butyl, or 2-ethylhexyl), or mixturesthereof; and

(c) 0 wt % to 10 wt % (or 0 wt % to 5 wt %, or 0.1 to 2 wt %) of anitrogen-containing monomer.

In one embodiment the star polymer may be a poly(meth)acrylate(typically a polymethacrylate), the star polymer may be derived from amonomer composition comprising:

(a) 65 wt % to 95 wt % (or 65 wt % to 94.9 wt %) of an alkyl(meth)acrylate, wherein the alkyl group of the (meth)acrylate has 10 to30, or 10 to 20, or 12 to 18, or 12 to 15 carbon atoms, or mixturesthereof;

(b) 5 wt % to 30 wt % of an alkyl (meth)acrylate, wherein the alkylgroup of the (meth)acrylate has 1 to 9, or 1 to 4 carbon atoms (forexample methyl, butyl, or 2-ethylhexyl), or mixtures thereof; and

(c) 0 wt % to 5 wt % (or 0.1 to 2 wt %) of a nitrogen-containingmonomer.

The alkyl (meth)acrylate includes, for example, compounds derived fromsaturated alcohols, such as methyl (meth)acrylate, butyl (meth)acrylate,2-methylpentyl (meth)acrylate, 2-propylheptyl (meth)acrylate,2-butyloctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl(meth)acrylate, nonyl (meth)-acrylate, isooctyl (meth)acrylate, isononyl(meth)acrylate, 2-tert-butylheptyl (meth)acrylate, 3-isopropylheptyl(meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate,5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyl dodecyl(meth)acrylate, tridecyl (meth)acrylate, 5-methyltri decyl(meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate,hexadecyl (meth)acrylate, 2-methylhexadecyl (meth)acrylate, heptadecyl(meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate,eicosyl (meth)acrylate, cetyl eicosyl (meth)acrylate, stearyleicosyl(meth)acrylate, docosyl (meth)acrylate and/or eicosyltetratriacontyl(meth)acrylate; (meth)acrylates derived from unsaturated alcohols, suchas oleyl (meth)acrylate; and cycloalkyl (meth)acrylates, such as3-vinyl-2-butylcyclohexyl (meth)acrylate or bornyl (meth)acrylate.

The alkyl (meth)acrylates with long-chain alcohol-derived groups may beobtained, for example, by reaction of a (meth)acrylic acid (by directesterification) or methyl methacrylate (by transesterification) withlong-chain fatty alcohols, in which reaction a mixture of esters such as(meth)acrylate with alkyl groups of various chain lengths is generallyobtained. These fatty alcohols include Oxo Alcohol® 7911, Oxo Alcohol®7900 and Oxo Alcohol® 1100 of Monsanto; Alphanol® 79 of ICI; Nafol®1620, Alfol® 610 and Alfol® 810 of Condea (now Sasol); Epal® 610 andEpal® 810 of Ethyl Corporation; Linevol® 79, Linevol® 911 and Dobanol®25 L of Shell AG; Lial® 125 of Condea Augusta, Milan; Dehydad® andLorol® of Henkel KGaA (now Cognis) as well as Linopol® 7-11 and Acropol®91 of Ugine Kuhlmann.

In one embodiment the star polymer may be further functionalised in thecore or the polymeric arms with a nitrogen-containing monomer. Thenitrogen-containing monomer may be referred to as a dispersant monomer.The nitrogen-containing monomer may include a vinyl-substituted nitrogenheterocyclic monomer, a dialkylaminoalkyl (meth)acrylate monomer, adialkylaminoalkyl (meth)acrylamide monomer, a tertiary-(meth)acrylamidemonomer or mixtures thereof.

In one embodiment the core or polymeric arms further comprise a(meth)acrylamide or a nitrogen containing (meth)acrylate monomer.Examples of a suitable nitrogen-containing vinyl monomer includeN,N-dimethylacrylamide, N-vinyl carbonamides such as N-vinyl-formamide,vinyl pyridine, N-vinylacetoamide, N-vinyl-n-propionamides, N-vinylhydroxyacetoamide, N-vinyl imidazole, N-vinyl pyrrolidinone, N-vinylcaprolactam, dimethylaminoethyl acrylate (DMAEA),dimethylaminoethyl-methacrylate (DMAEMA), dimethyl aminobutylacrylamide,dimethylamino-propylmethacrylate (DMAPMA),dimethylamine-propyl-acrylamide, dimethyl-aminopropylmethacrylamide,dimethylaminoethyl-acrylamide, or mixtures thereof.

A dispersant monomer may also be oxygen-containing compound. Theoxygen-containing compound may include hydroxyalkyl (meth)acrylates suchas 3-hydroxypropyl (meth)acrylate, 3,4-dihydroxybutyl (meth)acrylate,2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,2,5-dimethyl-1,6-hexanediol (meth)acrylate, 1,10-decanediol(meth)acrylate, carbonyl-containing (meth)acrylates such as2-carboxyethyl (meth)acrylate, carboxymethyl (meth)acrylate,oxazolidinyl ethyl (meth)acrylate, N-(methacryloyloxy)formamide,acetonyl (meth)acrylate, N-methacryloylmorpholine,N-methacryloyl-2-pyrrolidinone,N-(2-methacryloyloxyethyl)-2-pyrrolidinone,N-(3-methacryloyloxypropyl)-2-pyrrolidinone,N-(2-methacryloyloxypentadecyl)-2-pyrrolidinone,N-(3-methacryloyloxyheptadecyl)-2-pyrrolidinone; glycoldi(meth)acrylates such as 1,4-butanediol (meth)acrylate, 2-butoxyethyl(meth)acrylate, 2-ethoxyethoxymethyl (meth)acrylate, 2-ethoxyethyl(meth)acrylate, or mixtures thereof.

Other examples of suitable non-carbonyl oxygen containing compoundscapable of being incorporated into the copolymer include (meth)acrylatesof ether alcohols, such as tetrahydrofurfuryl (meth)acrylate,vinyloxyethoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate,1-butoxypropyl (meth)acrylate, 1-methyl-(2-vinyloxy)ethyl(meth)acrylate, cyclo-hexyloxymethyl (meth)acrylate, methoxymethoxyethyl(meth)acrylate, benzyloxymethyl (meth)acrylate, furfuryl (meth)acrylate,2-butoxyethyl (meth)acrylate, 2-ethoxyethoxymethyl (meth)acrylate,2-ethoxyethyl (meth)acrylate, allyloxymethyl (meth)acrylate,1-ethoxybutyl (meth)acrylate, methoxymethyl (meth)acrylate,1-ethoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate andethoxylated (meth)acrylates which typically have 1 to 20, or 2 to 8,ethoxy groups, or mixtures thereof.

Substantially Linear Polymer

The composition of the invention includes a substantially linear polymerwith a weight average molecular weight of 45,000 or less, or 35,000 orless, or 25,000 or less, or 8000 to 25,000, or 12,000 to 20,000.

The substantially linear polymer may be a copolymer comprising unitsderived from monomers (i) an α-olefin and (ii) an ethylenicallyunsaturated carboxylic acid or derivatives thereof esterified with analcohol. In one embodiment, the substantially linear polymer may be acopolymer comprising units derived from monomers (i) one or more alphaolefins and (ii) one or more alkyl (meth)acrylate esters. Theethylenically unsaturated carboxylic acid may be esterified with alcoholbefore or after polymerisation with the α-olefin. In one embodiment theethylenically unsaturated carboxylic acid may be esterified with alcoholbefore polymerisation with the α-olefin. In one embodiment theethylenically unsaturated carboxylic acid may be esterified with alcoholafter polymerisation with the α-olefin.

A commercially available copolymer prepared by esterification beforepolymerisation is available from Akzo Nobel sold under the tradenameKetjenlube®3700. The alcohol may have 1 to 40, or 1 to 30, or 4 to 20,or 6 to 16 carbon atoms. Examples of a suitable alcohol include2-ethylhexanol, 2-butyloctanol, 2-hexyldecanol, 2-octyldodecanol,2-decyltetradecanol, butanol, pentanol, hexanol, heptanol, octanol,nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol,pentadecanol, hexadecanol, heptadecanol, octadecanol, eicosanol, ormixtures thereof. A copolymer of this type is described in more detailin U.S. Pat. No. 4,526,950, or 6,419,714, or 6,573,224, or 6,174,843.

The ethylenically unsaturated carboxylic acid may be esterified withalcohol after polymerisation with the α-olefin. A copolymer of this typemay be a substantially linear polymer that may in one embodiment be (a)a copolymer comprising units derived from monomers (i) an α-olefin and(ii) an ethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher position,wherein the copolymer typically has a reduced specific viscosity of upto 0.2, (b) a poly(meth)acrylate, or mixtures thereof.

The substantially linear polymer may be present in the compositionsdescribed herein at 0.1 wt % to 50 wt %, or 2 wt % to 40 wt %, or 5 wt %to 30 wt %, or 8 wt % to 20 wt % of the lubricating composition. Incertain embodiments the lubricating composition contains 0.3 to 15 wt %of star polymer and 1 to 35 wt % of substantially linear polymer. Inother embodiments, the lubricating composition contains 0.45 to 5 wt %of star polymer and 2 to 25 wt % of substantially linear polymer.

Linear Poly(meth)acrylate

In one embodiment the substantially linear polymer includes apoly(meth)acrylate, or mixtures thereof.

In one embodiment the substantially linear polymer includes apoly(meth)acrylate (typically a polymethacrylate) with units derivedfrom a mixture of alkyl (meth)acrylate ester monomers containing, (a) 8to 24, or 12 to 18, or to 15 carbon atoms in the alcohol-derived portionof the ester group and (b) 6 to 11, or 8 to 11, or 8 carbon atoms in thealcohol-derived portion of the ester group, and which have 2-(C₁₋₄alkyl)-substituents, and optionally, at least one monomer selected fromthe group consisting of (meth)acrylic acid esters containing 1 to 7carbon atoms in the alcohol-derived portion of the ester group and whichare different from (meth)acrylic acid esters (a) and (b), vinyl aromaticcompounds (or vinyl aromatic monomers); and nitrogen-containing vinylmonomers such as those disclosed above; provided that no more than 60%by weight, or no more than 50% by weight, or no more than 35% by weightof the esters contain not more than 10 carbon atoms in thealcohol-derived portion of the ester group. The linear polymer of thistype is described in more detail in U.S. Pat. No. 6,124,249, or EP 0 937769 A1 paragraphs [0019] and [0031] to [0067]. (The “alcohol-derivedportion” refers to the “—OR” portion of an ester, when written asR′C(═O)—OR, whether or not it is actually prepared by reaction with analcohol.) Optionally, the linear polymer may further contain a thirdmonomer. The third monomer may be styrene, or mixtures thereof. Thethird monomer may be present in an amount 0% to 25% of the polymercomposition, or from 1% to 15% of the composition, 2% to 10% of thecomposition, or even from 1% to 3% of the composition.

Typically, the mole ratio of esters (a) to esters (b) in the copolymerranges from 95:5 to 35:65, or 90:10 to 60:40, or 80:20 to 50:50.

The esters are usually aliphatic esters, typically alkyl esters. In oneembodiment the ester of (a) may be a C₁₂₋₁₅ alkyl methacrylate and theester of (b) may be 2-ethylhexyl methacrylate.

In one embodiment, the ester groups in ester (a) contain branched alkylgroups. The ester groups may contain 2 to 65%, or 5 to 60% of the estergroups having branched alkyl groups.

The C₁₋₄ alkyl substituents may be methyl, ethyl, and any isomers ofpropyl and butyl.

The weight average molecular weight of the poly(meth)acrylate may be45,000 or less, or 35,000 or less, or 25,000 or less, or 8000 to 25,000,or 12,000 to 20,000.

Copolymer of (i) α-Olefin and (ii) an Ethylenically UnsaturatedCarboxylic Acid or Derivatives Thereof

In one embodiment the substantially linear polymer includes a copolymercomprising units derived from monomers (i) an α-olefin and (ii) anethylenically unsaturated carboxylic acid or derivatives thereofesterified with a primary alcohol branched at the β- or higher position,wherein the copolymer typically has a reduced specific viscosity of upto 0.2, or up to 0.15, or up to 0.10, or up to 0.08. In one embodimentthe reduced specific viscosity may be up to 0.08 (or 0.02 to 0.08 (or0.02 to 0.07, 0.03 to 0.07 or 0.04 to 0.06).

A measurement correlating with molecular weight of the copolymer (orinterpolymer such as an alternating copolymer) may be expressed in termsof the “reduced specific viscosity” of the copolymer which is arecognised means of expressing the molecular size of a polymericsubstance. As used herein, the reduced specific viscosity (abbreviatedas RSV) is the value typically obtained in accordance with the formulaRSV=(Relative Viscosity−1)/Concentration, wherein the relative viscosityis determined by measuring, by means of a dilution viscometer, theviscosity of a solution of 1.6 g of the polymer in 100 cm³ of acetoneand the viscosity of acetone at 30° C. For purpose of computation by theabove formula, the concentration is adjusted to 1.6 g of the copolymerper 100 cm³ of acetone. A more detailed discussion of the reducedspecific viscosity, also known as the specific viscosity, as well as itsrelationship to the average molecular weight of a copolymer, appears inPaul J. Flory, Principles of Polymer Chemistry, (1953 Edition) pages 308et seq.

In one embodiment the copolymer may be derived from monomers (i) anα-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof,

wherein 0.1 to 99.89 percent of the carboxylic acid units are esterifiedwith a primary alcohol branched at the β- or higher position,

wherein 0.1 to 99.89 percent of the carboxylic acid units are esterifiedwith a linear alcohol or an alpha-branched alcohol (e.g, a secondaryalcohol),

wherein 0.01 to 10% of the carboxylic acid units has at least one of anamino-, amido- and/or imido-group, and

wherein the copolymer has a reduced specific viscosity (prior toesterification) of up to 0.08.

In one embodiment the copolymer may be derived from monomers (i) anα-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof,

wherein 0.1 to 99.89 percent of the carboxylic acid units are esterifiedwith a primary alcohol branched at the β- or higher position,

wherein 0.1 to 99.9 percent of the carboxylic acid units are esterifiedwith a linear alcohol or an alpha-branched alcohol,

wherein 0 to 10% of the carboxylic acid units has at least one of anamino-, amido- and/or imido-group, and

wherein the copolymer has a reduced specific viscosity of up to 0.08.

A linear alcohol may include methanol, ethanol, propanol, butanol,pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol,dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol,heptadecanol, octadecanol, nonadecanol, eicosanol, or mixtures thereof.In one embodiment the linear alcohol contains 6 to 30, or 8 to 20, or 8to 15 carbon atoms (typically 8 to 15 carbon atoms).

The linear alcohol may include commercially available materials such asOxo Alcohol® 7911, Oxo Alcohol® 7900 and Oxo Alcohol® 1100 of Monsanto;Alphanol® 79 of ICI; Nafol® 1620, Alfol® 610 and Alfol® 810 of Condea(now Sasol); Epal® 610 and Epal® 810 of Ethyl Corporation (now Afton);Linevol® 79, Linevol® 911 and Dobanol® 25 L of Shell AG; Lial® 125 ofCondea Augusta, Milan; Dehydad® and Lorol® of Henkel KGaA (now Cognis)as well as Linopol® 7-11 and Acropol® 91 of Ugine Kuhlmann.

In one embodiment the copolymer may be derived from monomers (i) anα-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof,

wherein 5 to 15 percent of the carboxylic acid units are esterified witha primary alcohol branched at the β- or higher position,

wherein 0.1 to 95 percent of the carboxylic acid units are esterifiedwith a linear alcohol or an alpha-branched alcohol,

wherein 0 to less than 2% of the carboxylic acid units has at least oneof an amino-, amido- and/or imido-group, and

wherein the copolymer has a reduced specific viscosity of up to 0.08.

In one embodiment the copolymer comprises units derived from monomers(i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof esterified with a primary alcohol branched at the β-or higher position. In certain embodiments the copolymer may berepresented by the formula below. Ester or other groups with the primaryalcohol-derived moiety branched at the β- or higher position may berepresented within the (shown in the formula:

wherein

-   -   Formula (I) may comprise a copolymer backbone (BB), and one or        more pendant groups as shown, wherein BB may be derived from a        copolymer of (i) an α-olefin and (ii) an ethylenically        unsaturated carboxylic acid or derivatives thereof (typically        fumaric acid, maleic anhydride, maleic acid, (meth)acrylic acid,        itaconic anhydride or itaconic acid);    -   X may be a functional group which either (i) contains a carbon        and at least one oxygen or nitrogen atom (such as an ester or        amide, or imide linkage), or (ii) is an alkylene group with 1 to        5 carbon atoms (typically —CH₂—), connecting the copolymer        backbone and a branched hydrocarbyl group contained within (        )_(y), (typically X may be X may be a functional group which        either (i) contains a carbon and at least one oxygen or nitrogen        atom);    -   w may be the number of pendant groups attached to the copolymer        backbone, which may be in the range of 2 to 2000, or 2 to 500,        or 5 to 250;    -   y may be 0, 1, 2 or 3, provided that in at least 1 mol % of the        pendant groups, y is not zero; and with the proviso that when y        is 0, X is bonded to a terminal group in a manner sufficient to        satisfy the valence of X, wherein the terminal group is selected        from hydrogen, alkyl, aryl, a metal (typically introduced during        neutralisation of ester reactions. Suitable metals include        calcium, magnesium, barium, zinc, sodium, potassium or lithium)        or ammonium cation, and mixtures thereof;    -   p may be an integer in the range of 1 to 15 (or 1 to 8, or 1 to        4); and    -   R′ and R″ may independently be linear or branched hydrocarbyl        groups, and the combined total number of carbon atoms present in        R′ and R″ may be at least 12 (or at least 16, or at least 18 or        at least 20).

In different embodiments the copolymer with pendant groups may contain0.10% to 100%, or 0.5% to 20%, or 0.75% to 10%, branched hydrocarbylgroups represented by a group within ( )_(y) of the formula above,expressed as a percentage of the total number of pendant groups. (Thependant groups of formula (1) may also be used to define the estergroups as defined above by the phrase “esterified with a primary alcoholbranched at the β- or higher position”).

In different embodiments the functional groups defined by X on theformula above, may comprise at least one of —CO₂—, —C(O)N═ or—(CH₂)_(v)—, wherein v is an integer in the range of 1 to 20, or 1 to10, or 1 to 2.

In one embodiment X may be derived from an ethylenically unsaturatedcarboxylic acid or derivatives thereof. Examples of a suitablecarboxylic acid or derivatives thereof typically include maleicanhydride, maleic acid, (meth)acrylic acid, itaconic anhydride oritaconic acid. In one embodiment the ethylenically unsaturatedcarboxylic acid or derivatives thereof may be at least one of maleicanhydride or maleic acid.

In one embodiment X is other than an alkylene group, connecting thecopolymer backbone and the branched hydrocarbyl groups.

In different embodiments the pendant groups may be esterified, amidatedor imidated functional groups.

In one embodiment the pendant groups may be derived from esterifiedand/or amidated functional groups.

In one embodiment the copolymer includes esterified pendant groups. Thependant groups may be derived from Guerbet alcohols. The Guerbetalcohols may contain 10 to 60, or 12 to 60, or 16 to 40 carbon atoms. Inone embodiment the primary alcohol branched at the β- or higher positiondescribed herein may be a Guerbet alcohol. Methods to prepare Guerbetalcohols are disclosed in U.S. Pat. No. 4,767,815 (see column 5, line 39to column 6, line 32).

Examples of suitable groups for R′ and R″ on the formula defined aboveinclude the following:

1) alkyl groups containing C₁₅₋₁₆ polymethylene groups, such as 2-C₁₋₁₅alkyl-hexadecyl groups (e.g. 2-octylhexadecyl) and 2-alkyl-octadecylgroups (e.g. 2-ethyloctadecyl, 2-tetradecyl-octadecyl and2-hexadecyloctadecyl);

2) alkyl groups containing C₁₃₋₁₄ polymethylene groups, such as 1-C₁₋₁₅alkyl-tetradecyl groups (e.g. 2-hexyltetradecyl, 2-decyltetradecyl and2-undecyltridecyl) and 2-C₁₋₁₅ alkyl-hexadecyl groups (e.g.2-ethyl-hexadecyl and 2-dodecylhexadecyl);

3) alkyl groups containing C₁₀₋₁₂polymethylene groups, such as 2-C₁₋₁₅alkyl-dodecyl groups (e.g. 2-octyldodecyl) and 2-C₁₋₁₅ alkyl-dodecylgroups (2-hexyldodecyl and 2-octyldodecyl), 2-C₁₋₁₅ alkyl-tetradecylgroups (e.g. 2-hexyltetradecyl and 2-decyltetradecyl);

4) alkyl groups containing C₆₋₉polymethylene groups, such as 2-C₁₋₁₅alkyl-decyl groups (e.g. 2-octyldecyl) and 2,4-di-C₁₋₁₅ alkyl-decylgroups (e.g. 2-ethyl-4-butyl-decyl group);

5) alkyl groups containing C₁₋₅ polymethylene groups, such as2-(3-methylhexyl)-7-methyl-decyl and2-(1,4-dimethylbutyl)-5,7,7-trimethyl-octyl groups; and

6) and mixtures of two or more branched alkyl groups, such as alkylresidues of oxoalcohols corresponding to propylene oligomers (fromhexamer to undecamer), ethylene/propylene (molar ratio 16:1-1:11)oligomers, iso-butene oligomers (from pentamer to octamer), C₅₋₁₇α-olefin oligomers (from dimer to hexamer).

The pendant groups may contain a total combined number of carbon atomson R′ and R″ in the range of 12 to 60, or 14 to 50, or 16 to 40, or 18to 40, or 20 to 36.

Each of R′ and R″ may individually contain 5 to 25, or 8 to 32, or 10 to18 methylene carbon atoms. In one embodiment the number of carbon atomson each R′ and R″ group may be 10 to 24.

Examples of suitable primary alcohol branched at the β- or higherposition include 2-ethylhexanol, 2-propyl heptanol, 2-butyloctanol,2-hexyldecanol, 2-octyldodecanol, 2-decyltetradecanol, or mixturesthereof.

The ethylenically unsaturated carboxylic acid or derivatives thereof maybe an acid or anhydride or derivatives thereof that may be whollyesterified, partially esterified or mixtures thereof. When partiallyesterified, other functional groups include acids, salts or mixturesthereof. Suitable salts include alkali metals, alkaline earth metals ormixtures thereof. The salts include lithium, sodium, potassium,magnesium, calcium or mixtures thereof. The unsaturated carboxylic acidor derivatives thereof includes acrylic acid, methyl acrylate,methacrylic acid, maleic acid or anhydride, fumaric acid, itaconic acidor anhydride or mixtures thereof, or substituted equivalents thereof.

Suitable examples of the ethylenically unsaturated carboxylic acid orderivatives thereof include itaconic anhydride, maleic anhydride, methylmaleic anhydride, ethyl maleic anhydride, dimethyl maleic anhydride ormixtures thereof.

In one embodiment the ethylenically unsaturated carboxylic acid orderivatives thereof includes maleic anhydride or derivatives thereof.

Examples of an alpha-olefin include 1-decene, 1-undecene, 1-dodecene,1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene1-octadecene, or mixtures thereof. An example of a useful alpha-olefinis 1-dodecene. The alpha-olefin may be a branched alpha-olefin, ormixtures thereof. If the α-olefin is branched, the number of carbonatoms of the α-olefin may range from 4 to 32, or 6 to 20, or 8 to 16.

In one embodiment the copolymer of the invention further includes anitrogen containing group such as those disclosed above. The nitrogencontaining group may be derived from a nitrogen containing compoundcapable of being incorporated during copolymerization. In one embodimentthe copolymer of the invention further includes a nitrogen containinggroup that may be capable of reacting with the functionalised copolymerbackbone, typically for capping the copolymer backbone. The capping mayresult in the copolymer having ester, amide, imide or amine groups. Thenitrogen group is described in more detail in paragraphs [0069] to[0087] of PCT Patent Application Number PCT/US09/052028, filed on Jul.29, 2009 by Price, Barton, Visger, entitled “Novel Copolymers andLubricating Compositions Thereof”.

In one embodiment the copolymer comprises units derived from monomers(i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof may be further reacted with an amine to additionallyprovide oxidation control. Typically, the copolymer with oxidationcontrol contains an incorporated residue of an amine-containing compoundsuch as morpholines, pyrrolidinones, imidazolidinones, acetamides,β-alanine alkyl esters, or mixtures thereof. Examples of suitablenitrogen-containing compounds include 3-morpholin-4-yl-propyl amine,3-morpholin-4-yl-ethylamine, β-alanine alkyl esters (typically alkylesters have 1 to 30, or 6 to 20 carbon atoms), or mixtures thereof.

In one embodiment the compounds based on imidazolidinones, cycliccarbamates or pyrrolidinones may be derived from a compound of generalstructure:

wherein

X=—OH or NH₂;

Hy″ may be hydrogen, or a hydrocarbyl group (typically alkyl, or C₁₋₄-,or C₂-alkyl);Hy may be a hydrocarbylene group (typically alkylene, or C₁₋₄-, or C₂—alkylene);Q=>NH, >NR, >CH₂, >CHR, >CR₂, or —O— (typically >NH, or >NR) andR may be C₁₋₄ alkyl.

In one embodiment the imidazolidinone includes1-(2-amino-ethyl)-imidazolidin-2-one (may also be calledaminoethylethyleneurea), 1-(3-amino-propyl)-imidazolidin-2-one,1-(2-hydroxy-ethyl)-imidazolidin-2-one,1-(3-amino-propyl)-pyrrolidin-2-one, 1-(3-amino-ethyl)-pyrrolidin-2-one,or mixtures thereof.

In one embodiment the copolymer may be reacted with an amine-containingcompound selected from morpholines, imidazolidinones, and mixturesthereof.

Oils of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity.Such oils include natural and synthetic oils, oil derived fromhydrocracking, hydrogenation, and hydrofinishing, unrefined, refined,re-refined oils or mixtures thereof. A more detailed description ofunrefined, refined and re-refined oils is provided in InternationalPublication WO2008/147704, paragraphs [0054] to [0056] (a similardisclosure is provided in US Patent Application 2010/197536, see [0072]to [0073]). A more detailed description of natural and syntheticlubricating oils is described in paragraphs [0058] to [0059]respectively of WO2008/147704 (a similar disclosure is provided in USPatent Application 2010/197536, see [0075] to [0076]). Synthetic oilsmay also be produced by Fischer-Tropsch reactions and typically may behydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodimentoils may be prepared by a Fischer-Tropsch gas-to-liquid syntheticprocedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in April2008 version of “Appendix E—API Base Oil Interchangeability Guidelinesfor Passenger Car Motor Oils and Diesel Engine Oils”, section 1.3Sub-heading 1.3. “Base Stock Categories”. In one embodiment the oil oflubricating viscosity may be an API Group II or Group III oil. In oneembodiment the oil of lubricating viscosity may be an API Group III baseoil (typically including hydrocracked/hydroisomerized base oil).

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 wt % the sum of the amountof the compound of the invention and the other performance additives.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention (comprising the additives disclosed herein) is in the form ofa concentrate which may be combined with additional oil to form, inwhole or in part, a finished lubricant), the ratio of the of theseadditives to the oil of lubricating viscosity and/or to diluent oilinclude the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 byweight.

Other Performance Additives

Compositions derived from the copolymer and/or lubricating compositionsdescribed herein optionally further includes other performanceadditives. The other performance additives comprise at least one ofmetal deactivators, detergents, dispersants, viscosity modifiers,friction modifiers, corrosion inhibitors, dispersant viscositymodifiers, antiwear agents, extreme pressure agents, antiscuffingagents, antioxidants, foam inhibitors, demulsifiers, pour pointdepressants, seal swelling agents and mixtures thereof. Typically,fully-formulated lubricating oil will contain one or more of theseperformance additives.

Dispersants

Dispersants are known and include for example an N-substituted longchain alkenyl succinimide, a Mannich base, or mixtures thereof. Examplesof N-substituted long chain alkenyl succinimides include polyisobutylenesuccinimide, wherein the polyisobutylene from which it is derived has anumber average molecular weight in the range 350 to 5000, or 500 to3000, or 750 to 1150.

The dispersants may also be post-treated by conventional methods by areaction with any of a variety of agents. Among these are boroncompounds (such as boric acid), urea, thiourea, dimercaptothiadiazoles,carbon disulphide, aldehydes, ketones, carboxylic acids such asterephthalic acid, hydrocarbon-substituted succinic anhydrides, maleicanhydride, nitriles, epoxides, and phosphorus compounds. In oneembodiment the post-treated dispersant is borated. In one embodiment thepost-treated dispersant is reacted with dimercaptothiadiazoles.

Detergents

Detergents are known and include neutral or overbased detergents, i.e.,ones prepared by conventional processes known in the art. Suitabledetergent substrates include, phenates, sulphur containing phenates,sulphonates, salixarates, salicylates, carboxylic acid, phosphorus acid,alkyl phenol, sulphur coupled alkyl phenol compounds, or saligenins. Inone embodiment the detergent includes a magnesium or calcium sulphonate,or mixtures thereof.

Antioxidant

Antioxidant compounds are known and include sulphurised olefins,diphenyl amines (such as dinonyl diphenyl amine), hindered phenols,molybdenum dithiocarbamates, and mixtures thereof. Antioxidant compoundsmay be used alone or in combination.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupis often further substituted with a hydrocarbyl group and/or a bridginggroup linking to a second aromatic group. Examples of suitable hinderedphenol antioxidants include 2,6-di-tert-butylphenol,4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol,4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenolantioxidant may be an ester and may include, e.g., Irganox™ L-135 fromCiba. Suitable examples of molybdenum dithiocarbamates which may be usedas an antioxidant include commercial materials sold under the tradenames such as Vanlube 822™ and Molyvan™ A from R. T. Vanderbilt Co.,Ltd., and Adeka Sakura-Lube™ S-100, S-165 and S-600 from Asahi DenkaKogyo K. K and mixtures thereof.

Viscosity Modifiers

In addition to the polymers described herein as part of the inventionthe lubricating composition may optionally further contain other knownviscosity modifiers. The viscosity modifiers may be hydrogenatedstyrene-butadiene rubbers, ethylene-propylene copolymers, hydrogenatedstyrene-isoprene polymers, hydrogenated diene polymers, polyalkylstyrenes, polyolefins, esters of maleic anhydride-styrene copolymers, ormixtures thereof.

Antiwear Agent

The lubricating composition optionally further includes at least oneantiwear agent. Examples of suitable antiwear agents include oil solubleamine salts of phosphorus compounds, sulphurised olefins, metaldihydrocarbyldithiophosphates (such as zinc dialkyldithiophosphates),thiocarbamate-containing compounds, such as thiocarbamate esters,thiocarbamate amides, thiocarbamic ethers, alkylene-coupledthiocarbamates, and bis(S-alkyldithiocarbamyl) disulphides.

In one embodiment the oil soluble phosphorus amine salt antiwear agentincludes an amine salt of a phosphorus acid ester or mixtures thereof.The amine salt of a phosphorus acid ester includes phosphoric acidesters and amine salts thereof; dialkyldithiophosphoric acid esters andamine salts thereof; amine salts of phosphites; and amine salts ofphosphorus-containing carboxylic esters, ethers, and amides; andmixtures thereof. The amine salt of a phosphorus acid ester may be usedalone or in combination.

In one embodiment the oil soluble phosphorus amine salt includes partialamine salt-partial metal salt compounds or mixtures thereof. In oneembodiment the phosphorus compound further includes a sulphur atom inthe molecule. In one embodiment the amine salt of the phosphoruscompound may be ashless, i.e., metal-free (prior to being mixed withother components).

The amines which may be suitable for use as the amine salt includeprimary amines, secondary amines, tertiary amines, and mixtures thereof.The amines include those with at least one hydrocarbyl group, or, incertain embodiments, two or three hydrocarbyl groups. The hydrocarbylgroups may contain 2 to 30 carbon atoms, or in other embodiments 8 to26, or 10 to 20, or 13 to 19 carbon atoms.

Primary amines include ethylamine, propyl amine, butylamine,2-ethylhexylamine, octylamine, and dodecylamine, as well as such fattyamines as n-octylamine, n-decylamine, n-dodecyl amine,n-tetradecylamine, n-hexadecylamine, n-octadecylamine and oleyamine.Other useful fatty amines include commercially available fatty aminessuch as “Armeen®” amines (products available from Akzo Chemicals,Chicago, Ill.), such as Armeen C, Armeen O, Armeen OL, Armeen T, ArmeenHT, Armeen S and Armeen SD, wherein the letter designation relates tothe fatty group, such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine,diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine,diheptylamine, methylethylamine, ethylbutylamine and ethyl amyl amine.The secondary amines may be cyclic amines such as piperidine, piperazineand morpholine.

The amine may also be a tertiary-aliphatic primary amine. The aliphaticgroup in this case may be an alkyl group containing 2 to 30, or 6 to 26,or 8 to 24 carbon atoms. Tertiary alkyl amines include monoamines suchas tert-butyl amine, tert-hexylamine, 1-methyl-1-amino-cyclohexane,tert-octylamine, tert-decylamine, tertdodecylamine,tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine,tert-tetracosanylamine, and tert-octacosanylamine.

In one embodiment the phosphorus acid amine salt includes an amine withC11 to C14 tertiary alkyl primary groups or mixtures thereof. In oneembodiment the phosphorus acid amine salt includes an amine with C14 toC18 tertiary alkyl primary amines or mixtures thereof. In one embodimentthe phosphorus acid amine salt includes an amine with C18 to C22tertiary alkyl primary amines or mixtures thereof.

Mixtures of amines may also be used in the invention. In one embodimenta useful mixture of amines is “Primene® 81R” and “Primene® JMT.”Primene® 81R and Primene® JMT (both produced and sold by Rohm & Haas)are mixtures of C11 to C14 tertiary alkyl primary amines and C18 to C22tertiary alkyl primary amines respectively.

In one embodiment oil soluble amine salts of phosphorus compoundsinclude a sulphur-free amine salt of a phosphorus-containing compoundmay be obtained/obtainable by a process comprising: reacting an aminewith either (i) a hydroxy-substituted di-ester of phosphoric acid, or(ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoricacid. A more detailed description of compounds of this type is disclosedin International Application PCT/US08/051126 (or equivalent to U.S.application Ser. No. 11/627,405).

In one embodiment the hydrocarbyl amine salt of an alkylphosphoric acidester is the reaction product of a C14 to C18 alkylated phosphoric acidwith Primene 81R™ (produced and sold by Rohm & Haas) which is a mixtureof C11 to C14 tertiary alkyl primary amines.

Examples of hydrocarbyl amine salts of dialkyldithiophosphoric acidesters include the reaction product(s) of isopropyl, methyl-amyl(4-methyl-2-pentyl or mixtures thereof), 2-ethylhexyl, heptyl, octyl ornonyl dithiophosphoric acids with ethylene diamine, morpholine, orPrimene 81R™, and mixtures thereof.

In one embodiment the dithiophosphoric acid may be reacted with anepoxide or a glycol. This reaction product is further reacted with aphosphorus acid, anhydride, or lower ester. The epoxide includes analiphatic epoxide or a styrene oxide. Examples of useful epoxidesinclude ethylene oxide, propylene oxide, butene oxide, octene oxide,dodecene oxide, and styrene oxide. In one embodiment the epoxide may bepropylene oxide. The glycols may be aliphatic glycols having from 1 to12, or from 2 to 6, or 2 to 3 carbon atoms. The dithiophosphoric acids,glycols, epoxides, inorganic phosphorus reagents and methods of reactingthe same are described in U.S. Pat. Nos. 3,197,405 and 3,544,465. Theresulting acids may then be salted with amines. An example of suitabledithiophosphoric acid is prepared by adding phosphorus pentoxide (about64 grams) at 58° C. over a period of 45 minutes to 514 grams ofhydroxypropyl 0,0-di(4-methyl-2-pentyl)phosphorodithioate (prepared byreacting di(4-methyl-2-pentyl)-phosphorodithioic acid with 1.3 moles ofpropylene oxide at 25° C.). The mixture may be heated at 75° C. for 2.5hours, mixed with a diatomaceous earth and filtered at 70° C. Thefiltrate contains 11.8% by weight phosphorus, 15.2% by weight sulphur,and an acid number of 87 (bromophenol blue).

The dithiocarbamate-containing compounds may be prepared by reacting adithiocarbamate acid or salt with an unsaturated compound. Thedithiocarbamate containing compounds may also be prepared bysimultaneously reacting an amine, carbon disulphide and an unsaturatedcompound. Generally, the reaction occurs at a temperature from 25° C. to125° C.

Examples of suitable olefins that may be sulphurised to form an thesulphurised olefin include propylene, butylene, isobutylene, pentene,hexane, heptene, octane, nonene, decene, undecene, dodecene, undecyl,tridecene, tetradecene, pentadecene, hexadecene, heptadecene,octadecene, octadecenene, nonodecene, eicosene or mixtures thereof. Inone embodiment, hexadecene, heptadecene, octadecene, octadecenene,nonodecene, eicosene or mixtures thereof and their dimers, trimers andtetramers are especially useful olefins. Alternatively, the olefin maybe a Diels-Alder adduct of a diene such as 1,3-butadiene and anunsaturated ester, such as, butylacrylate.

Another class of sulphurised olefin includes fatty acids and theiresters. The fatty acids are often obtained from vegetable oil or animaloil; and typically contain 4 to 22 carbon atoms. Examples of suitablefatty acids and their esters include triglycerides, oleic acid, linoleicacid, palmitoleic acid or mixtures thereof. Often, the fatty acids areobtained from lard oil, tall oil, peanut oil, soybean oil, cottonseedoil, sunflower seed oil or mixtures thereof. In one embodiment fattyacids and/or ester are mixed with olefins.

In an alternative embodiment, the ashless antiwear agent may be amonoester of a polyol and an aliphatic carboxylic acid, often an acidcontaining 12 to 24 carbon atoms. Often the monoester of a polyol and analiphatic carboxylic acid is in the form of a mixture with a sunfloweroil or the like, which may be present in the friction modifier mixturefrom 5 to 95, in several embodiments from 10 to 90, or from 20 to 85, or20 to 80 weight percent of said mixture. The aliphatic carboxylic acids(especially a monocarboxylic acid) which form the esters are those acidstypically containing 12 to 24, or from 14 to 20 carbon atoms. Examplesof carboxylic acids include dodecanoic acid, stearic acid, lauric acid,behenic acid, and oleic acid.

Polyols include diols, triols, and alcohols with higher numbers ofalcoholic OH groups. Polyhydric alcohols include ethylene glycols,including di-, tri- and tetraethylene glycols; propylene glycols,including di-, tri- and tetrapropylene glycols; glycerol; butane diol;hexane diol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose;cyclohexane diol; erythritol; and penta-erythritols, including di- andtripentaerythritol. Often the polyol is diethylene glycol, triethyleneglycol, glycerol, sorbitol, pentaerythritol or dipentaerythritol.

The commercially available monoester known as “glycerol monooleate” isbelieved to include 60±5 percent by weight of the chemical speciesglycerol monooleate, along with 35±5 percent glycerol dioleate, and lessthan 5 percent trioleate and oleic acid. The amounts of the monoesters,described above, are calculated based on the actual, corrected, amountof polyol monoester present in any such mixture.

Extreme Pressure Agents

Extreme Pressure (EP) agents that are soluble in the oil includesulphur- and chlorosulphur-containing EP agents, chlorinated hydrocarbonEP agents and phosphorus EP agents. Examples of such EP agents includechlorinated wax; sulphurised olefins (such as sulphurised isobutylene),organic sulphides and polysulphides such as dibenzyldisulphide,bis-(chlorobenzyl) disulphide, dibutyl tetrasulphide, sulphurised methylester of oleic acid, sulphurised alkylphenol, sulphurised dipentene,sulphurised terpene, and sulphurised Diels-Alder adducts;phosphosulphurised hydrocarbons such as the reaction product ofphosphorus sulphide with turpentine or methyl oleate; phosphorus esterssuch as the dihydrocarbon and trihydrocarbon phosphites, e.g., dibutylphosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenylphosphite; dipentylphenyl phosphite, tridecyl phosphite, distearylphosphite and polypropylene substituted phenol phosphite; metalthiocarbamates such as zinc dioctyldithiocarbamate and bariumheptylphenol diacid; amine salts of alkyl and dialkylphosphoric acids orderivatives including, for example, the amine salt of a reaction productof a dialkyldithiophosphoric acid with propylene oxide and subsequentlyfollowed by a further reaction with P₂O₅; and mixtures thereof (asdescribed in U.S. Pat. No. 3,197,405).

Corrosion inhibitors that may be useful in the compositions of theinvention include fatty amines, octyl octanamide, condensation productsof dodecenyl succinic acid or anhydride and a fatty acid such as oleicacid with a polyamine.

Foam inhibitors that may be useful in the compositions of the inventioninclude copolymers of ethyl acrylate and 2-ethylhexylacrylate andoptionally vinyl acetate; demulsifiers including trialkyl phosphates,polyethylene glycols, polyethylene oxides, polypropylene oxides and(ethylene oxide-propylene oxide) polymers.

Pour point depressants that may be useful in the compositions of theinvention include polyalphaolefins, esters of maleic anhydride-styrenecopolymers, poly(meth)acrylates, polyacrylates or polyacrylamides.

Friction modifiers that may be useful in the compositions of theinvention include fatty acid or fatty alkyl derivatives such as amines,esters, epoxides, fatty imidazolines, condensation products ofcarboxylic acids and polyalkylene-polyamines and amine salts ofalkylphosphoric acids. Other friction modifiers include fattyderivatives of hydroxyl carboxylic acids such as dialkyl tartrates,alkyl tartrimides, or citrate esters.

INDUSTRIAL APPLICATION

The method and lubricating composition of the invention may be suitablefor refrigeration lubricants, greases, gear oils, axle oils, drive shaftoils, traction oils, manual transmission oils, automatic transmissionoils, metal working fluids, hydraulic oils, or internal combustionengine oils.

In one embodiment the method and lubricating composition of theinvention may be suitable for at least one of gear oils, axle oils,drive shaft oils, traction oils, manual transmission oils or automatictransmission oils. In one embodiment the invention provides a method oflubricating a manual transmission.

An automatic transmission includes continuously variable transmissions(CVT), infinitely variable transmissions (IVT), toroidal transmissions,continuously slipping torque converter clutches (CSTCC), steppedautomatic transmissions or dual clutch transmissions (DCT).

The use (may also be referred to as a method) and copolymer compositiondescribed herein is capable of providing a lubricant with at least one(or at least two, or all) of acceptable or improved shear stability,acceptable or improved viscosity index control, acceptable or improvedoxidation control, and acceptable or improved low temperature viscosity.The copolymer may be employed as an oil of lubricating viscosity in thepresence or absence of other base oils.

When the copolymer with pendant groups further includes a nitrogencontaining compound, the copolymer may further have acceptable/improveddispersancy properties (cleanliness) and oxidation control.

The internal combustion engine may be a 2-stroke or 4-stroke engine.Suitable internal combustion engines include marine diesel engines,aviation piston engines, low-load diesel engines, and automobile andtruck engines.

In several embodiments a suitable lubricating composition includes thecopolymer present (on an actives basis) in ranges as shown in thefollowing table.

TABLE Embodiments (wt % of lubricant composition) A B C D Star Polymer0.1-30 2-30 5-20 8-15 Substantially Linear Polymer 0.1-50 2-40 5-30 8-20Other Performance Additives  0-15 0.01-15   0.5-10  0.5-10  Oil ofLubricating Viscosity    5-99.8  15-95.99  40-89.5  55-85.5 Embodiments(wt % of lubricant composition) E F G H Star Polymer 0.1-20 0.2-15 0.5-10  1-8  Substantially Linear Polymer 0.1-50 2-40 5-30 8-20 OtherPerformance Additives  0-15 0.01-15   0.5-10  0.5-10  Oil of LubricatingViscosity    5-99.7  15-97.79 40-94   55-90.5Footnote: The star polymer and the substantially linear polymer arethose described herein as part of the invention.

The weight percent of the star polymer and the substantially linearpolymer may also be in the following ranges 5 wt % to 20 wt % of starpolymer and 5 wt % to 15 wt % of the substantially linear polymer of thelubricating composition disclosed herein. The weight percent of the starpolymer and the substantially linear polymer may also be in thefollowing ranges 8 wt % to 15 wt % of star polymer and 5 wt % to 10 wt %of the substantially linear polymer of the lubricating compositiondisclosed herein.

The weight ratio of the star polymer to the substantially linear polymermay also vary from 6:1 to 1:1, or 4:1 to 1.1, or 3:1 to greater than2:1. A ratio closer to 2:1 may begin to become less shear stable thanratios greater than 2:1. In other embodiments, the ratio may be 0.02:1to 18:1, and in yet other embodiments, the ratios may be 0.04:1 to 9:1or 0.1:1 to 4:1 or 0.2:1 to 2:1. The following examples provide anillustration of the invention. These examples are non exhaustive and arenot intended to limit the scope of the invention.

EXAMPLES

Star Polymers 1 to 13 (SP1 to SP13): Polymers are the same as thosedisclosed on page 32, paragraph [0100] of International Publication WO2006/047393 (equivalent to US Publication 2009-0118150) respectively,except monomer B (as is shown in Table 9 of WO 2006/047393) is methylmethacrylate.

Substantially linear polymers 1 to 8 (SLP1 to SLP8) with a weightaverage molecular weight of 45,000 or less are disclosed inInternational Application PCT/US09/052028 (filed 29 Jul., 2009 by Bartonet al., now WO2010/014655) respectively; see examples Cpp1 to Cpp8 inparagraphs [0140] and [0141].

Comparative Example 1 (CE1) is a manual transmission lubricant based onan API Group III base oil further containing 0.45 wt % of one or morecorrosion inhibitors, 0.75 wt % of one or more antioxidants, 0.68 wt %of one or more antiwear agents, 0.62 wt % of one or more detergents, 1.5wt % of one or more dispersants, 1 wt % of one or more pour pointdepressant, 0.02 wt % of one or more antifoam agent and 20 wt % of thecopolymer of SLP1.

Comparative Example 2 (CE2) is manual transmission lubricant similar toCE1, except it contains 16 wt % of the polymer of SP11.

Invention lubricant 1 (INVL1) is a manual transmission lubricant similarto CE1, except the copolymer of SLP1 is present at 11 wt % and thepolymer of SP13 is present at 10 wt %.

The manual transmission lubricants are evaluated using the followingtest procedures: ASTM D445 (Kinematic Viscosity (KV) at 40° C. and 100°C., ASTM D2983 (Brookfield Viscosity (BV) are determined at −40° C.),D2270 (Viscosity Index (VI)), KRL tapered bearing shear stability test(KRL Test), and an Energy Loss test

The lubricating compositions are subjected to shear as determined by KRLtapered bearing shear stability test employing a 4-ball wear testinstrument as is used in CEC DIN 51350 Part 6 test procedure. Theinstrument is run for 20 hours with a 5000 N load, at 140° C. and at1450 rpm. The viscosity data obtained from the test is described in ASTMmethod D445.

Energy loss data and maximum temperature of gearbox are measured as isdescribed below. A transverse 5-speed gearbox modified by locking thegear differential in fourth gear. The gearbox input is driven by anelectric motor and the output load applied by a dynamometer; the size ofeach should be suitable for the test profile. The gear box is mounted ina temperature controlled environment, capable of maintaining atemperature of −7° C. The gearbox is pre-soaked at −7° C. for at least60 minutes. The low power NEDC test cycle is used throughout the test.The input speed for the NEDC cycle is calculated to match the correctoutput/road speed using available tyre diameters and gear ratios. In asimilar manner the applied load is calculated from the NEDC test cycleusing the assumptions of a medium sector passenger car, tyre diameter,and gear ratios. The output from the test is the sump temperature andenergy absorbed at the end of each stage. These are measure via athermocouple in the gearbox sump and input/output torque transducers.The test is performed in triplicate. The results reported are theaverage based on the three runs. Typically better results are obtainedfor samples with a lower temperature at the end of stage 5, and forsamples with lower energy loss values.

The results obtained for viscometrics evaluations are:

CE1 CE2 INVL1 D445 at 100° C. (mm²/s) 9.03 8.37 8.48 D445 at 40° C.(mm²/s) 46.2 28.4 33.0 D2983 at −40° C. (mm²/s) 43,400 12,020 14,640 VI181 196 251 KRL Test Kinematic Viscosity 8.64 6.08 6.89 at 100° C. afterKRL Shear (mm²/s) Viscosity Loss 4.42 27.36 18.94 After Shear Test (%)

The results obtained for energy loss and maximum temperature (° C.) are:

CE1 CE2 INVL1 Stage 1 Loss (kJ) 86.3 58.1 54.8 Stage 2 Loss (kJ) 76.856.2 51.1 Stage 3 Loss (kJ) 69.8 53.3 48.3 Stage 4 Loss (kJ) 66.6 52.247.4 Stage 5 Loss (kJ) 283.7 242.5 221 Total Energy Loss (kJ) 44.9 38.234.4 Stage 1 Maximum −1.8 −3.9 −4.1 Temperature (° C.) Stage 2 Maximum1.2 −2 −2.3 Temperature (° C.) Stage 3 Maximum 3.2 −0.6 −1.1 Temperature(° C.) Stage 4 Maximum 4.5 0.4 −0.1 Temperature (° C.) Stage 5 Maximum15.2 9.6 8.7 Temperature (° C.)

The results indicate that the example of the invention has an improvedshear stability, has lost less energy and has reduced operatingtemperature compared to either of the comparative examples.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. The productsformed thereby, including the products formed upon employing lubricantcomposition of the present invention in its intended use, may not besusceptible of easy description. Nevertheless, all such modificationsand reaction products are included within the scope of the presentinvention; the present invention encompasses lubricant compositionprepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. However, the amount of each chemical component ispresented exclusive of any solvent or diluent oil, which may becustomarily present in the commercial material, unless otherwiseindicated. It is to be understood that the upper and lower amount,range, and ratio limits set forth herein may be independently combined.Similarly, the ranges and amounts for each element of the invention maybe used together with ranges or amounts for any of the other elements.

As used herein, the term “(meth)acrylic” and related terms includes bothacrylic and methacrylic groups.

As used herein, the term “a primary alcohol branched at the β- or higherposition” relates to an alcohol with branching at the 2-position or ahigher position (e.g., 3-, or 4-, or 5-, or 6-, or 7-position etc.)

As used herein the number of carbon atoms present in the ester groups ofthe polymers of the invention is counted to include only those carbonatoms of the alcohol-derived portion of the ester group. Specifically,the number of carbon atoms excludes the carbonyl carbon of the ester.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude: hydrocarbon substituents, including aliphatic, alicyclic, andaromatic substituents; substituted hydrocarbon substituents, that is,substituents containing non-hydrocarbon groups which, in the context ofthis invention, do not alter the predominantly hydrocarbon nature of thesubstituent; and hetero substituents, that is, substituents whichsimilarly have a predominantly hydrocarbon character but contain otherthan carbon in a ring or chain. A more detailed definition of the term“hydrocarbyl substituent” or “hydrocarbyl group” is described inparagraphs [0118] to [0119] of International Publication WO2008147704 (asimilar description of hydrocarbyl is also described in paragraphs[0137] to [0141] of published application US 2010-0197536.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A lubricating composition comprising (a) an oilof lubricating viscosity, (b) a star polymer, and (c) a substantiallylinear polymer with a weight average molecular weight of 45,000 or less,wherein the substantially linear polymer is a copolymer comprising unitsderived from monomers (i) an α-olefin and (ii) an ethylenicallyunsaturated carboxylic acid or derivatives thereof esterified with aprimary alcohol branched at the β- or higher position.
 2. Thelubricating composition of claim 1, wherein the substantially linearpolymer has a weight average molecular weight of 8000 to 25,000.
 3. Thelubricating composition of claim 1, wherein the substantially linearpolymer has a weight average molecular weight of 12,000 to 20,000. 4.The lubricating composition of claim 1, wherein the substantially linearpolymer is a copolymer derived from monomers (i) an α-olefin and (ii) anethylenically unsaturated carboxylic acid or derivatives thereof,wherein 0.1 to 99.89 percent of the carboxylic acid units are esterifiedwith a primary alcohol branched at the β- or higher position, wherein0.1 to 99.89 percent of the carboxylic acid units are esterified with alinear alcohol or an alpha-branched alcohol, wherein 0.01 to 10% of thecarboxylic acid units has at least one of an amino-, amido- and/orimido-group, and wherein the copolymer has a reduced specific viscosityof up to 0.08.
 5. The lubricating composition of claim 1, wherein thecopolymer, prior to esterification has a reduced specific viscosity ofup to 0.15.
 6. The lubricating composition of claim 5, wherein thesubstantially linear polymer prior to esterification has a reducedspecific viscosity of 0.02 to 0.07.
 7. The lubricating composition ofclaim 5, wherein the substantially linear polymer prior toesterification has a reduced specific viscosity of 0.04 to 0.06.
 8. Thelubricating composition of claim 1, wherein the substantially linearpolymer is present at 5 wt % to 30 wt % of the lubricating composition.9. The lubricating composition of claim 1, wherein the substantiallylinear polymer is a copolymer comprising units derived from monomers (i)an α-olefin and (ii) an ethylenically unsaturated carboxylic acid orderivatives thereof esterified with a primary alcohol branched at the β-or higher position; and wherein the substantially linear polymer ispresent at 5 wt % to 30 wt % of the lubricating composition.
 10. Thelubricating composition of claim 1, wherein the ethylenicallyunsaturated carboxylic acid or derivatives thereof is at least one ofmaleic anhydride or maleic acid.
 11. The lubricating composition ofclaim 1, wherein the star polymer is a poly(meth)acrylate, and whereinthe star polymer is derived from a monomer composition comprising: (a)50 wt % to 100 wt % of an alkyl (meth)acrylate, wherein the alkyl groupof the (meth)acrylate has 10 to 20 carbon atoms, or mixtures thereof;(b) 0 wt % to 40 wt % of an alkyl (meth)acrylate, wherein the alkylgroup of the (meth)acrylate has 1 to 9 carbon atoms, or mixturesthereof; and (c) 0 wt % to 10 wt % of a nitrogen-containing monomer. 12.The lubricating composition of claim 1, wherein the star polymer is apoly(meth)acrylate, and wherein the star polymer is derived from amonomer composition comprising: (a) 65 wt % to 95 wt % of an alkyl(meth)acrylate, wherein the alkyl group of the (meth)acrylate has 12 to18 carbon atoms, or mixtures thereof; (b) 5 wt % to 30 wt % of an alkyl(meth)acrylate, wherein the alkyl group of the (meth)acrylate has 1 to9, carbon atoms, or mixtures thereof; and (c) 0 wt % to 5 wt % of anitrogen-containing monomer.
 13. The lubricating composition of claim 1,wherein the star polymer is a polymethacrylate and is present at 2 wt %to 30 wt % of the lubricating composition
 14. The lubricatingcomposition of claim 1, wherein the star polymer is a polymethacrylateand present at 5 wt % to 20 wt %, of the lubricating composition. 15.The lubricating composition of claim 1, wherein the star polymer is apolymethacrylate and is present at 0.5 to 10 wt % of the lubricatingcomposition.
 16. The lubricating composition of claim 1, wherein thelubricating composition contains 0.3 wt % to 15 wt % of star polymer and1 wt % to 35 wt % of the substantially linear polymer.
 17. Thelubricating composition of claim 1, wherein the lubricating compositioncontains 0.45 wt % to 5 wt % of star polymer and 2 wt % to 25 wt % ofthe substantially linear polymer.
 18. A method of lubricating amechanical device comprising supplying to the device lubricatingcomposition of claim
 1. 19. The method of claim 18, wherein themechanical device is a manual transmission.
 20. The method of claim 18,wherein the mechanical device is an automatic transmission.